1. Field of the Invention
The present invention relates to an electronic musical instrument, and more particularly to an electronic musical instrument capable of applying a musical effect such as the slur, portamento, etc. to a musical tone.
2. Prior Art
The "slur" is one of the performance methods, by which the current note changes to the next note in such a manner that its tone pitch is smoothly varied. Therefore, when the slur is effected, the current tone pitch is not directly changed to the next tone pitch.
Recently, several kinds of electronic musical instruments have been developed in such a way that the above-mentioned slur can be automatically applied to the musical tone (see Japanese Patent Publication No. 63-4191, corresponding to U.S. Pat. No. 4,524,668). Such electronic musical instrument provides a slur switch. When a ligature performance operation (i.e., a key operation in which the second key is to be depressed before the depressing first key is released) is carried out in the state where the slur switch is on, the conventional electronic musical instrument automatically effects the slur, by which the first note (corresponding to the first key) smoothly changes to the second note (corresponding to the second key) in such a manner that the interval is smoothly varied.
In the typical electronic musical instrument, the slur is effected in such a manner that the interval is varied linearly. On the other hand, some electronic musical instruments can vary the interval along an exponentially curved line. This curved line is called as the slur curve along which the interval, tone volume, etc. are smoothly varied. However, the number of slur curves should be limited to only one in the conventional electronic musical instrument. In other words, there is a problem in that the conventional electronic musical instrument cannot vary the interval and the like along the free curve.
In addition, when the slur is effected, the tone volumes of the slurred notes are varied in such a manner that the first tone volume (corresponding to the key-depression intensity of the first note in the slurred notes) is linearly varied to the second tone volume (corresponding to the key-depression intensity of the last note in the slurred notes), which makes the conventional slur effect monotonous.
Further, when the slur is effected, tone pitches are sequentially varied in the slurred notes. However, the musical tone waveform itself is not varied. As a result, it seems that the similar notes having the similar waveforms are sequentially sounded by merely varying their tone pitches in the conventional electronic musical instrument.